This invention relates to a stripping mechanism for removing drawn or extruded hollow articles from a press ram. More specifically, this invention relates to stripping mechanisms of the type with a stripper supporting ring holding several strippers distributed along the circumference of the press ram with each of these strippers being movable radially in the direction toward the axis of the press ram and away therefrom, as well as individually in the direction of the press ram axis.
In a conventional apparatus of this type (German Pat. No. 593,849), several bearing segments are mounted in a stripper supporting ring to be movable in the direction of the axis of the press ram, and respectively one stripper is disposed in each bearing segment to be movable within limits in the radial direction. In this construction, the bearing segments are under the effect of compression springs with respect to the stripper supporting ring and the strippers are under the effect of compression springs with respect to the associated bearing segments. These compression springs, on the one hand, urge the bearing segments in the direction toward the stripping edge of the hollow article and, on the other hand, urge the strippers inwardly in the radial direction. One disadvantage of this conventional arrangement resides in that hardly more than one stripper can be mounted in each bearing segment. The apparatus thus is composed of many individual parts and therefore becomes susceptible to malfunction if it is desired to provide numerous strippers distributed along the circumference of the press ram in order to obtain a favorable force transmission to the stripping edge of the hollow article during the stripping thereof.
Another conventional apparatus (German Pat. No. 1,285,973) for the stripping of deep-drawn hollow articles from a press ram includes a stripper bearing ring and several strippers distributed over the circumference of the press ram. These strippers are of a segment shape and each stripper is pivotable within limits in its plane in directions toward and away from the press ram and is also movable within limits in the direction of the axis of the press ram. In this system, all strippers are under the effect of two elastic rings, one of which elastically supports all strippers during the stripping step in the direction of the axis of the press ram with respect to the stripper bearing ring, and the other of which, surrounding all strippers together, urges the strippers to pivot radially toward the inside. One disadvantage in this construction is the very limited elastic movability of the individual strippers in the direction of the axis of the press ram.
Both above-described, conventional constructions have the disadvantage in common, first of all, that the elastic forces effective on the individual strippers in the direction of the axis of the press ram and radially inwardly cannot be adapted to the respectively ambient working conditions without exchanging the springs or rings. This has the consequence, with regard to the displacements in the direction of the axis of the press ram, that the intended adaptation of the position of the individual strippers to the shape of the stripping edge, changing from one hollow article to the other, is obtained during the stripping process only if the resistance offered by the hollow article against the stripping action is in a range corresponding to the elasticity of the springs or of the ring. In case the resistance is too small or too large, the conventional devices, however, are ineffective since either there is no compression of the ring or springs at all, or a complete compression up to the rear end position of the springs or of the ring takes place. Corresponding remarks apply for the radial displacements or pivotal movements of the strippers regarding the force with which the strippers contact the hollow article while the press ram with the hollow article passes through, so that the surface of the article may be damaged. Another disadvantage of the above-described conventional arrangements resides in that no means are provided therein, or could be provided therein in a simple manner, for displacing the bearing segments and together therewith the strippers in cyclic or rhythmic operation positively in the radial direction toward the outside so as to make it possible for the press ram with the hollow article to pass through without any contact during the working cycle of the press ram.
The present invention contemplates constructing the bearing of the bearing segments and of the strippers so that the elastic forces with which the strippers contact the stripping edge of the hollow article during the stripping step can be adapted in a simple manner to the respective resistance offered by the hollow article during the stripping step, and that simultaneously a displaceablility of the individual strippers in the direction of the axis of the press ram can be attained to a relatively large extent. This construction makes it possible under all conditions which may arise for the strippers to contact the irregularly shaped stripping edge of the hollow article without appreciable deformation, thus effecting the stripping step.
The invention further contemplates a construction wherein several bearing segments are disposed in a stripper supporting ring to be radially displaceable to a limited extent; wherein at least one stripper is mounted in each bearing segment to be displaceable within limits in the direction of the press ram axis; wherein each stripper includes an external operating piston and an internal stripping piston connected therewith, the inner surface of the latter forming a part of the inner surface of the bearing segment, a stripping end face of this internal stripping piston being extendable out of the end face of the bearing segment facing the hollow article during the stripping step; and wherein the end face of the operating piston facing away from the stripping end face of the stripping piston is connected with a controllable source of a pressure medium.
A particularly simple preferred embodiment of this invention is obtained by mounting, in the stripper supporting ring, three bearing segments encompassing each a sector angle of about 120.degree., and by arranging in each bearing segment several strippers disposed at equal spacings from one another. Three bearing segments can be supported in the stripper supporting ring in a relatively advantageous manner, wherein numerous strippers can suitably be distributed over the circumference of the press ram.
In order to simplify the feeding of pressure medium to the strippers, the feature is provided according to the invention that a connection duct is arranged in each bearing segment, terminating at the end faces of all operating pistons mounted therein which are exposed to the pressure medium. This connection duct is in communication with a pressure medium feed source.
This invention contemplates several preferred embodiments with various means for evoking radial displacements of the bearing segments with respect to the stripper supporting ring.
One preferred embodiment includes at least one spring engaging the bearing segments which displace these segments radially inwardly by elastic action. The inner surfaces of the bearing segments are beveled conically toward the outside at the end facing away from the stripping end faces of the stripping pistons. In this arrangement, the bearing segments are each shifted radially toward the outside by the hollow article by means of the beveled surface each time the press ram with the hollow article passes through. This mode of operation can also be attained in another embodiment wherein each bearing segment contains at least one pressure medium space of variable volume in communication with the pressure medium source. Radially outward boundary surfaces of this space being formed by the stripper supporting ring so that the pressure medium continuously applies a radially inward force on the bearing segments. As in the embodiment with the spring, the inner surfaces of the bearing segments have an outwardly pointing, conical bevel at the end facing away from the stripping end faces of the stripping pistons. These two embodiments are especially suitable for devices for the stripping off of such hollow articles wherein the external surface is not particularly sensitive so that the continuous radially inward biasing forces on said bearing segments does not damage the external surface during passage of the hollow articles.
However, for devices to strip off hollow articles having a very sensitive outer surface, more suitable embodiments of the invention are provided wherein the bearing segments are forcibly displaced alternatingly radially outwardly and inwardly in correspondence with the operating and stripping cycles of the press ram.
A preferred embodiment with forcible alternating radial displacement of the bearing segments includes at least one spring engaging the bearing segments and moving same elastically radially toward the outside. Respectively one roller, rotatably mounted in each bearing segment, contacts in the radial direction a guide track on the outside, which track is arranged in a guide ring moving about the axis of the press ram and rotatably disposed in the stripper supporting ring. This track effects the rhythmically alternating movements of the bearing segments radially inwardly and makes it possible for such movements to take place radially outwardly in response to the spring forces as well. In this arrangement, the guide track has, in each case, a number of inwardly and outwardly pointing beveled or inclined ramp surfaces between circular sections with two different radii which corresponds to the number of bearing segments provided. Another modification of this arrangement resides in that each bearing segment consists of an outer part carrying the roller, which outer part is also engaged by the spring effecting the radially outward displacement, and of an inner part carrying the strippers. This inner part is radially movable within limits with respect to the outer part and a compression spring is located between the outer part and the inner part. By the division of each bearing segment into an outer part and an inner part, an exact contact of the inner part with the strippers at the press ram is facilitated during the stripping step.
The effect of alternating, positive radial displacements of the bearing segments toward the inside and toward the outside can also be attained according to another preferred embodiment of the invention by providing that each bearing segment contains at least one pressure medium space of variable volume in communication with the pressure medium feed source. The boundary surface of this space, which is disposed inwardly in the radial direction, is connected with the stripper supporting ring. Respectively one roller mounted rotatably to each bearing segment contacts in the radial direction on the outside a guide track provided in a guide ring moving about the axis of the press ram and rotatably disposed in the stripper supporting ring, which guide track effects the rhythmically alternating displacements of the bearing segments radially inwardly and makes it possible for such displacements to take place radially outwardly as well. Also in this embodiment, the guide track has inclined surfaces between circular sections.
The effect of alternating, positive radial displacements can also be attained according to yet another preferred embodiment of the invention with the use of two corresponding guide tracks at the guide ring. Two rollers are mounted at each bearing segment with one of these rollers contacting respectively one guide track on the outside in the radial direction and the other of these rollers contacting respectively the other guide track on the inside in the radial direction. The guide tracks are located on a guide ring revolving about the axis of the press ram and rotatably mounted in the stripper supporting ring to effect rhythmically alternating displacements of the bearing segments radially inwardly and outwardly. In a further modification of this embodiment each bearing segment includes an outer part carrying the rollers and an inner part radially displaceable within limits with respect to the outer part and carrying the strippers. A compression spring is arranged between the outer part and the inner part. This provides additionally the effect attainable by the division of the bearing segments described above for another embodiment.
These and further objects, features and advantages of the present invention will become more obvious from the following description when taken in connection with the accompanying drawings which show, for purposes of illustration only, several embodiments in accordance with the present invention.